One of President Trump’s core promises prior to winning the election was that he would work to make America’s borders safer and crack down on illegal immigration. There is evidence surfacing every day showing not only that he is working on this problem, but that people have been entering America illegally for a long time.

US Customs and Border Protection reports that in San Diego, they discovered a small tunnel on Saturday that resulted in the arrest of 30 people who were crossing the border illegally. Of the 30 people, 23 were Chinese nationals, and the other seven were from Mexico. The opening was a hole with a ladder in it that led around and featured an exit around the second fence on the Otay Mesa entrance of the country.

While there are multiple tunnel systems going through the Mexican-California border point, many are not used to bring people in. Rather, in most cases, they are used to smuggle drugs and contraband.

The fact that a tunnel was discovered harboring 30 people leads many officials to believe that this is just one of many. The CBP posted a picture of the tunnel on their Twitter page.

One look at the tunnel and it’s evident that it has been in use for quite some time. This is not something new that was just used for the first time. It runs a mile underground.

It’s difficult to estimate how many people have come through this tunnel into the United States. US Customs is investigating the occurrence to try and find out how many others have used this as their “path to citizenship,” as illegal as it may be.

Now, the US is working with their Mexican counterparts to monitor the area and prevent other people from coming through until the tunnel is closed off. Many believe that this tunnel is part of an extension that would meet with a previously incomplete tunnel.

If US Customs can shut down all of the tunnels leading to the US, immigration would drop significantly. President Trump has said that he hopes to step up the current immigration plan and try to keep out as many unlawful immigrants as possible.

According to Fox News, immigration officials were not able to capture everyone who was in the tunnel. Some back peddled and fled back into Mexico, while others submitted and went peacefully.

The fact that Chinese nationals were discovered in this tunnel show that there is a new trend emerging–immigrants from countries well beyond Mexico are using tunnels like these to infiltrate America’s borders. In order to increase the country’s safety, these tunnels will need to be closed off, and frequent monitoring for signs of new tunnels will need to be performed. It is unknown at the time how the Chinese and Mexican nationals discovered the tunnel.

There must be joint action from US Customs and their Mexican counterparts to ensure that borders are enforced. This will help protect the United States from unlawful, undocumented immigration, and could potentially save lives from the treacherous conditions found in many of these tunnels.